The present invention relates to domestic water heaters and especially to a partitioning water heater tank member for stratifying the water in the tank in a predetermined pattern.
Domestic water heaters have been used for many years, and generally are composed of a tank connected to a cold water inlet by a tube to the bottom of the tank and a hot water outlet connected to the top of the tank. One or two heating elements are disposed in the tank for heating the water contained therein. The lower heating element provides the majority of the heating responsive to the lower thermostat, while the upper element responds to a thermostat located in the upper one-third of the tank and provides a quick recovery of heated water when most of the hot water in the tank has been drawn off. The response time in heating the top portion of the tank and thus providing renewed hot water is extended in the typical tank design because of the induced mixing of the heated water rising off of the heating element with the water below the element drawn up in a circular pattern. Prior patents dealing with thermal stratification may be seen in U.S. Pat. No. 4,253,446 to B. Muller, which divides a solar storage reservoir between the solar collected energy and the auxiliary heater with an opening pipe directly under the auxiliary heater. A Patent to R. G. Fleet, U.S. Pat. No.: 3,546,429, also provides thermal stratification of the water in the tank. A Patent to H. E. Thomason, U.S. Pat. No.: 4,369,764, shows a first hot water heater inside a second hot water used in conjunction with a solar heater. A Patent to J. W. Andrews, U.S. Pat. No.: 4,390,008, has a sliding disk mounted in a hot water heater for partially dividing a hot water tank, while U.S. Pat. No.: 4,357,932 to W. Dodd Stacy has a fixed divider in a solar heating system. These devices have the disadvantage of causing an internal circulation within the tank whenever the hot water rising from the heating element is not drawn out of the top port so that the mixing or destratification has the net effect of greater heat loss from the tank than would be the case in a well stratified tank. Greater heat loss occurs along the walls of the tank so that maintaining cooler water stratified adjacent the walls minimizes the loss through the heater walls. Thermal stratification has increased significance when a tank and back up heating element are coupled to a solar heating system.
Single tank solar water heating systems are generally classified as direct or indirect. Those that utilize a non-freezing circulation fluid, to collect heat when passing through the collector and then add heat to the storage tank when passed through a heat exchanger, located within the storage tank are referred to as indirect systems. Systems that circulate the tank potable water directly through the solar panel are referred to as direct systems. In a single tank solar system, the lower element is replaced with a heat exchange coil in the indirect system while the direct system allows direct circulation of water to the solar absorber. These existing tank configurations have the disadvantage that the circulation of a direct connected solar system mixes the temperature of gradients within the solar tank, reducing the efficiency of the collector system. Such mixing is also induced by the hot water rising from a solar heat exchanger of the indirect type. Prior U.S. Pat. No.: 4,253,446 utilizes a separating wall with two flow orifices, one of which utilizes a tube to direct rising or falling water with the intent of enhancement of thermal stratification within the tank. This Patent has the disadvantage of enhancing the natural circulation throughout the entire tank caused by the backup element. Colder water from the lower tank section is drawn up through the orifice adjacent the back up element to replace the heated water rising from the element. This in turn draws down water through the second orifice and tube, thereby mixing the water in the tank in a circulating fashion. The drawn down water is usually warmer than the temperature of the existing water in the bottom of the tank, and this mixing defeats the stratification of the tank divider.
An aim of the present invention is to construct a baffle of such design that it may be readily inserted into a hot water tank during its manufacture to produce stratification by naturally rising hotter water directed towards the center of the tank where it is insulated by the cooler water near the tank walls. Any cooler naturally falling water is directed towards the tank wall where it can insulate the hotter water stratified towards the center of the tank. Lateral mixing motion is induced by the solar circulation pump or water being drawn from the tank top with colder replacement water entering the bottom, or by the heating element cycling on it's thermostat. This invention prohibits the mixing of the entire tank and disrupting whatever thermal stratification exist. Such mixing is limited to the area of the tank enclosed by the tank walls and the partition placed therein. A divider properly placed below the upper heating element of the tank prohibits the circulation throughout the tank caused by the heating elements cycling and thus provides a more rapid recovery of heated water available for use than would be otherwise experienced in a tank of typical construction.